The artificial insemination of dairy cows and other domestic animals is an important procedure in the dairy and other livestock industries. Knowledge of the available time for breeding is also desired for herdsmen when natural breeding is planned. In many species of domesticated and wild animals the female animal must be inseminated during or shortly after a relatively brief period of sexual receptivity to achieve conception. This period of sexual receptivity is referred to alternatively as the estrous period, estrus, or heat.
In cattle, the estrous period occurs approximately every 21 days in nonpregnant females. Estrus in cattle lasts for a relatively short 12-24 hour period, during which time the cows must be inseminated in order to become pregnant. In modern dairy farming cows are typically inseminated artificially. In dairy cattle, pregnancy is necessary to bring about physiological changes which provide for the onset of milk production. After an initial pregnancy, dairy cows are preferably maintained pregnant to insure milk production. In beef cattle, control over the timing of pregnancy for the production of calves is very important, especially for range cattle. Lost time between calving is also of significant economic importance to beef cattle herdsmen.
It is known that cattle exhibit several behavioral and physiological characteristics which are specific to the estrous phase of their cycles, or which occur very near estrus. Physiological indications that an animal is in estrus include increased blood flow to the reproductive tract, changes in the impedance of reproductive tract fluids, elevated body temperature, and changes in blood hormone levels.
Behavior indications that cattle are in estrus include nervousness, increased physical activity and mobility, and increased vocalization (bawling). Cattle also exhibit certain behavior associated with mounting. During estrus there is an increased frequency of mounting of other cattle by the animal in heat. Another characteristic of estrus in cattle which is particularly important to this invention is that cows in heat will allow themselves to be mounted and remain mounted by other cattle. This behavior termed "standing to be mounted" is mating behavior exhibited by the cow in heat. Although cattle are mounted by other cattle at times outside of estrus, cows will maintain a relatively prolonged mounted standing posture during estrus. When cattle are not in estrus, they will not allow prolonged mounting by other cattle in the herd, and will walk out from under a cow or bull which is attempting to mount. This behavior has given rise to the term "standing heat" which indicates the period of actual estrus during which fertilization and conception can occur and the cow will stand to be mounted. During or approaching heat, cattle also place their chins on the hindquarters of the cow to determine if she will stand to be mounted. Standing to be mounted is also an indication of estrus in other animal species, such as sheep.
Prior attempts and systems for detection of estrus in cattle have not proven satisfactory. One approach involved placing pedometers on the legs of cows in order to measure increased movement and locomotive activity. This approach has proven to be inaccurate because increased physical activity can occur for a variety of reasons and can vary from one animal to another to a significant degree. Another prior attempt at detecting estrus in cattle involved the routine insertion of vaginal probes. The vaginal probes contained sensors which detected changes in the electrical resistivity of the vaginal mucus discharge. This method has proven undesirable due to the excessive manpower requirements for conducting the tests, and problems with maintaining sanitation and health of the cattle.
Several prior attempts to detect and signal the onset of estrus in cattle were premised upon the increased mounting behavior exhibited toward cows in heat. The Kamar heat mount detector and other similar units include the placement of special dye containers on the backs of cattle being monitored. When the animal in heat is mounted, the dye in the container is pressed from a reservoir into a viewing cylinder, thus providing a visible indicator of estrus. This technique results in a large number of false positives, apparently due to the spurious mounting of cows which are not in heat. Additionally, each device may be used only once and must be routinely and manually installed and removed from the cattle. This requires substantial amounts of time and effort on the part of herdsmen. Furthermore, the dye containers are difficult to attach on the hindquarters of cattle so that they will not be lost when the animal is mounted.
U.S. Pat. No. 4,206,766 discloses a mechanical device which is tripped by mounting behavior upon a cow wearing the device. This type of device is difficult to maintain in the desired position and requires examination of each cow wearing the device to determine if mounting has occurred. It is also prone to false tripping due to spurious mounting.
A somewhat different approach is shown in U.S. Pat. No. 3,824,989 to Horner et al. This patent shows a device which is mounted on a bull using a collar or harness and includes a marker which applies marking material to cows in heat. If the bull is not desired in the herd, too busy, or predisposed to certain cows, then the suitability and reliability of this approach decreases substantially. It also is subject to being dislodged from the bull and failure to provide a visually recognizable mark on the cows. This method also relies on the sexual interest or drive of the marking animal which is subject to substantial variation. Similar marking devices can also be installed on penal deviated bulls, penectomized bulls, estrogenized or androgenized cows.
Another technique which has been used is chalking of the tailheads of cows being monitored. This approach involves applying a grease crayon-like mark to the tailhead of the cow. Upon receiving mounting activity the mark disappears. This approach suffers from significant amounts of error, in part arising from the necessity of interpreting the presence or absence of the grease crayon from the animals hide. Other activities can cause the marking to disappear. This method also consumes substantial amounts of time since each cow being monitored must be marked daily. The application of the marking is further troublesome because the cows must be secured in a stanchion during application of the marking.
Another approach to cattle estrous detection is shown in U.S. Pat. No. 4,411,274 to Wright. The Wright patent discloses an electronic apparatus which is attached to the back of a female animal and transmits a signal when the animal is mounted by another animal. The maintenance of such a detector on the cow is difficult and subject to repeated loss of time and equipment.
A further approach to estrous detection is shown in U.S. Pat. No. 4,635,587 to Leonardo which discloses a saddle-like device which fits over the hindquarters of a cow. This device includes a sleeve for carrying an apparatus which includes both an electronic timer and indicator that are activated when the cow is mounted by another cow. The timer records the amount of time which has elapsed since the cow was mounted. A herdsman must visually identify the indicator and then read the mounting time information. It is also difficult to maintain the apparatus in the desired position on the cow.
U.S. Pat. No. 3,844,273 to Polsen discloses an apparatus which is attached to the back of an animal either by glue, straps, or a harness. Polsen's apparatus is also activated by the mounting of the animal, and a transmitter signal and timer are turned on. The transmitted signal is detected and the time information is then obtained from the unit.
Despite these numerous and long felt attempts, none of these prior art approaches has satisfactorily solved the problem of how to reliably and efficiently detect estrus, particularly in cattle. The approaches utilizing a detector which is connected to the animal being monitored for estrus have consistently suffered problems. These problems often are associated with the difficulty of maintaining the detection apparatus either on the leg or hindquarters of the animal. Prior to this time no one has solved this pervasive problem. The detecting apparatuses must remain attached regardless of the movement of the animal and contact with other animals and objects. This has often necessitated careful supervision and monitoring by the herdsman. Such monitoring is an additional chore not appreciated.
Many of the prior art devices also suffer problems associated with the need for routine monitoring by the herdsman. For example, timers must be read from the devices on the backs of individual animals in the patents to Leonardo and Polsen. Dye containers must be carefully inspected to discern whether mounting has occurred. The visual identification of detector status or information requires in most cases requires the careful inspection of the cow's detector. This consumes substantial amounts of time in large herds and often makes such estrous detection systems impractical, particularly on modern dairy farms where the number of herdsmen are minimized and milking and feeding work must be completed quickly. Thus it is apparent that automated estrous detection systems are needed in the livestock industries.
Another limitation of the prior art is the failure to continuously monitor estrus. Many of the prior techniques require routine maintenance or operation, such as installation of a new dye container, supplying new marking material, adjustment or repositioning of a mounted detector, or reading of the indicator to assess whether estrus has occurred. Such maintenance or operation often results in lapses in monitoring because of the unintended absence, replacement or removal of the detection device. Accordingly, there is a substantial problem associated with missing estrus because of the non-continuous operation of the prior art heat detection techniques.
A further problem of the prior art concerns the incorrect diagnosis of estrus for animals not truly in estrus. All of the prior art described hereinabove which relies upon mounting behavior fails to distinguish between non-estrous mounting and estrous mounting. Since cattle in a herd periodically mount one another as routine behavior, such as when the mounting cow is in heat, failure to discriminate cows in standing heat from those incidentally mounted can cause substantial losses in time and increased costs associated with artificially inseminating non-fertile cows. Erroneous estrous diagnosis and associated artificial insemination can also lead to removal of estrous monitoring devices, thus causing a later true estrus to not be identified. This in turn causes at least one cycle to be missed and places an increased burden on the herdsman to diagnose for conception or additional cycles can be lost. Thus it can be appreciated that false indications can be particularly disadvantageous and costly.
Because of limitations and inadequacies, such as indicated above, the prior art estrous detection systems have not been well received by the cattle or dairy industries. For these reasons visual observation of cow behavior continues to be the primary technique used to determine estrus in cattle. However, only about 50% of the cows displaying behavioral indications of estrus are detected by human visual monitoring. Of the cows selected by visual observation, about 10-30% are not actually in heat. The faulty diagnosis of heat typically results from the absence of the observer, infrequent or careless observation, or to a lesser extent, because of only subtle behavioral manifestations of heat. Because of the high rates of error in visual observation and diagnosis, there are very substantial opportunities for improving the detection of heat in cattle and providing increased productivity as a result of such detection.
There remains a strong need for accurate, reliable, timely and economical systems and detectors for diagnosing estrus in cattle and similar animals exhibiting standing heat behavior.